Door air screen



June 14', 1966 E. LARSON ETAL DOOR AIR SCREEN Filed Jan, 15, 1964INVENTOR5 EUGENE 4/7250 5704.?7' PAUL 40/1/00 W X/VM free/W976 UnitedStates Patent DUOR AIR SCREEN Eugene Larson, Milibrae, and Stuart PaulLondon, San

Carlos, Califi, assiguors to National Industrial Equipment Co., acorporation Filed .lan. 15, 1964, Ser. No. 337,942 3 Claims. ((11. 9836)Our invention relates to an improved version of a device adapted to bemounted over a doorway and effective to blow air downwardly over thedoorway opening in order to prevent the ingress of insects and debrisfrom outside and to permit the passage of people and goods through thedoorway, all without requiring the use of a door panel. A related deviceis shown in Patent 3,086,441.

In previous installations of door air screens, it has been observedthat, without having a high velocity air stream, it is difficult toarrange the flow of air in such a way as to ensure that insects and thelike flying from the outside cannot penetrate the doorway. In the eventonly goods are to go through the doorway, then a high velocity-airstream is not objectionable, but in the event people pass through thedoorway, the velocity of the stream must be limited to an amount whichis not unpleasant to the doorway users.

Also, and particularly where retail work is carried on as distinguishedfrom wholesale shipping and the like, the noise level of the apparatusand the kinds of noise generated by the apparatus are of considerableimportance.

White noise and some high pitched noises as given off :by some devicesare annoying to customers and do not make the entranceway or doorwayinviting.

It is therefore an object of the invention to provide a 8 door airscreen arranged in such a way as to afford a relatively large volume oflow velocity air, relatively, so that external penetration by insectsand the like is precluded, yet use of the doorway by customers ispleasant.

Another object of the invention is to provide a door air screen in whichmeans are provided for varying the flow of the air stream from thescreen not only longitudinally of the doorway, but also transverselythereof in order that the air flow pattern can be made most effectiveand least unpleasant for the particular installation.

Another object of the invention is to provide a relatively simple andstraightforward door air screen in which many of the sounds arisingin-the motor and fan mechanism are not readily amplified, but, on thecontrary, are damped and suppressed so that the operating noise level ofthe structure and the nature of the emitted sound are satisfactory andnot obtrusive.

Another object of the invention is to provide a door air screen whichcan simply and easily be manufactured and serviced.

Another object of the invention is in general to provide an improveddoor air screen.

Other objects together with the foregoing are attained in the embodimentof the invention described in the ac companying description andillustrated in the accompanying drawings, in which:

FIGUREl is a side elevation of a door air screen in a typicalinstallation on the exterior of a doorway, portions of the doorway beingshown in cross section;

FIGURE 2 is a front elevation of the door air screen shown in FIGURE 1;

FIGURE 3 is a crosssection on a transverse vertical plane through thedoor air screen of the invention;

FIGURE 4 is a cross section similar to FIGURE 3 but taken on a verticallongitudinal plane through the door air screen;

FIGURE 5 is a detail in plan of some of the hexagonal I cellularmaterial used in the lateral deflector panels; and FIGURE 6 is a detailshowing in elevation from below the appearance of a means for rigidlyjoining the shrouds. While the door air screen can be incorporated in anumber of different ways, it is typically embodied as shown herein foruse on a vertical, planar wall 4 having 1 pair of vertical side panels19 and 21. These panels are all generally planar and are arranged toform a rectangular enclosure entirely open at the top and at the bottom.The housing is mounted on the wall by fastenings 5 on the rear panel 18.

Within the housing so formed and extending generally horizontallytherein is a diaphragm plate 22. This is usually fabricated of lightmetal and is appropriately secured in place, for example by spot weldingor the like. The diaphragm plate 22 extends entirely between the sidepanels 19 and 21 and entirely between the front and rear panels 17 and18 so as to define an upper compartment 23 and a distinct lowercompartment 24 within the housing. The diaphragm plate is provided witha pair of circular openings 26 and 27 affording communication betweenthe upper and lower compartments 23 and 24. The circular openings areeach bounded by one of a pair .of shrouds 28 and 29. These convenientlyare circular cylindrical flanges secured to the diaphragm plate 22 anddepending for a substantial distance into the compartment 24.

Spanning the interior of the upper compartment 23 and overlying theopenings 26 and 27 are support beams 31 and 32 preferably in the form ofchannels disposed with their Webs uppermost and their flanges dependingdownwardly. In some instances, the support beams are formed integrallywith the diaphragm plate 22. When the support beams are separatemembers, it is preferred to fasten them and thediaphragm plate togetherquite rigidly so that they do not move or vibrate relatively to eachother, but rather serve as stiffening reinforcements for each other. Atappropriate intervals, the beams 31 and 32 are provided with fastenings33 which pass through and are secured to the diaphragm plate.

As an additional means for affording beam strength and for impartingconsiderable additional rigidity to the diaphragm plate assembly, weespecially provide a connector 34 secured to the adjacent portions ofthe lower margin of the shrouds 28 and 29. In effect, the beams 31 and32, the diaphragm plate 22 and the deeply extending circular cylindricalshrouds 28 and 29' are joined by the connector 34 to afford a beamstructure virtually of the rigidity of a single beam having the samedepth as the vertical dimension of the beams 31 and 32 and together withthe verticaldimension of the shrouds 28 and 29.

An extremely stiff support is thus afforded for a pair of electricmotors 41 and 42, each resting upon and being fastened to the beams 31and 32 by appropriate fastening bolts 43. Each of the motors has one ofa pair of depending shafts 44 and 46 centralized with respect to theopenings 26 and 27 and serving as a drive and support for the respectiveone of a pair of fans 47 and 48 disposed within the .individual shrouds28 and 29. Preferably, the motors 41 and 42 are both driven in the samedirection of rotation, so that the fans 47 and 48 are identical. Thefans when operated are effective to blow an air current through thehousing from the upper open end thereof and outwardly and downwardlythrough the lower open end thereof. If the downward air currents aresimply left to impinge upon the generally horizontal floor 12, they tendto eddy and flow in various directions including directions havingsubstantial components toward the doorway 6. Insects, such as flies,which appear in some portion of the downward stream are then actuallycarried into and through the doorway rather than being kept outsidethereof.

To obviate this effect, the housing is preferably provided with a pairof panels 51 and 52. These are substantially alike. Each panel is arectangular structure comprised of a plurality of hexagonal cells 53.Customarily, these are formed of stiff paper or thin aluminum orcomparable material and serve as means for channeling and directing thehelically and vortically swirling air discharged by the fans into ahomogeneous parallel flow with a major downward component and onlyslight eddies. The fact that the two fans 47 and 48 may operate in thesame or opposite directions is not important since the eddies from thevortical flow of the air discharged by the fans are straightened andcancelled by the hexagonal panel materials. The air flow below thepanels is practically rectilinear.

The reduction of eddy currents is best accomplished by locating thepanels 51 and 52 quite close to the fans 47 and 48 but not so close asto induce any sound or siren effects. This easily can be accomplished insubstantially the way illustrated in FIGURES 3 and 4. Preferably, thepanels 51 and 52 at their adjacent portions rest on flange projections54 at the bottom of the housing and also rest upon adjusting screws 56passing through lips 57 projecting inwardly into the housing. When thescrews 56 are appropriately adjusted, the panels 51 and 52 arepreferably both inclined to form a dihedral angle so that there is adirection or component given to the air transversely or laterally of thedoorway opening 6 and generally parallel to the plane of the wall 4.Thus, air flowing downwardly and having passed through the panels 51 and52 and impinging upon the planar floor 12 has flow components directedoutwardly or away from the doorway in lateral directions and thus tendsto repel any otherwise inflowing material.

The air flow is likewise controlled by a plurality of louvers 61. Eachof these is conveniently made of a metal envelope having a stream-linedor airfoil cross section and is mounted at its opposite ends on securingpivots 62 and 63 in 21 depending collar frame 64 detachably secured tothe housing 16. The louvers 61 are substantially in abutment at theirends with friction washers 65 so that the louvers can readily beoriented or directed about the pivotal axes of thefastenings 62 and 63and can be pointed more or less outwardly of the doorway. When thelouvers have been properly adjusted during installation, the fastenings62 and 63 are secured and the louvers are then frictionally held in aninclined attitude. The collar frame at its forward and rearward walls isaugmented by guide plates 66 and 67 so that between the respective guideplates and the adjacent louvers appropriate venturi-form throats areafforded. The louvers 61 are set more or less at an inclination to thevertical in such a way that downflowing air does not impinge upon thefloor 12 perpendicularly.

4 Rather, the air stream is given an outward horizontal or repellingcomponent so that upon approaching or striking the floor the air flow isoutwardly and thus repels insects or debris which might tend otherwiseto travel inwardly of the air screen.

In the operation of the device, the air is sometimes inducted into thehousing without any baflle or screen, but in most instances it ispreferred to provide a framework 68 around the upper margins of thehousing in order that one or more filter plates 69 can movably bepositioned therein. The filters are not intended to exclude allparticles, but are merely to restrain larger items which might tend toclog the panels 51 and 52. The filters also have an acoustic effect, asdoes the hexagonal cellular panelling 51 and 52, tending to prevent thespread of sound. The incoming air passes over and tends to cool themotors and then flows through the fans 47 and 48. The air flow isrelatively quiet and the operation of the motors is likewise quiet sinceit has been found that by connecting the entire structure together quiterigidly and especially by joining the shrouds by the connector 34 toprovide a deep beam, the period of vibration is reduced substantially toa subsonic level or at least to pleasant frequencies. The sound is notat high, annoying frequencies which are easily amplifiied anddisseminated by relatively free, sheet metal parts.

The air flowing from the fans traverses the cellular panels 51 and 52.This not only affords a rectilinear flow in a downward direction, butalso substantially cancels eddy currents. This itself tends markedly toreduce the noise. Further reduction is caused by some absorption by thecellular material, particularly if it is paper. The inclined panels 51and 52 impart transverse components to the air, following which the airthen passes between the louvers 61 imparting an outward component to theair. The resulting air blast in striking the floor tends to spread outor diverge outwardly. Thus insects, such as flies, are incapable ofpenetrating the downwardly flowing current, although the velocitythereof is not so great as to interfer with or become unpleasant tocustomers. While insects flying into the curtain may have sufficientvelocity to penerate part way, yet the thickness and width of thecurtain are so great that before the insects can penetrate into theinterior and through the doorway, they are forced downwardly toward andagainst the floor 12 and then blown outwardly away therefrom. A personpassing through the doorway 6 and being subjected to the downwardlyflowing relatively broad curtain of air does not have any disturbingimpingement since the velocity of the flow is relatively low over arelatively long and wide area.

The net result of the structure, therefore, is to provide a door airscreen which operates quietly and effectively to keep out flyinginsects, debris and rubbish from the outside, yet is not unpleasant forthe passage of people through the doorway 6 in either direction.

What is claimed is:

1. A door air screen for use on'a wall over a doorway comprising ahousing having a vertical front panel, a vertical rear panel, a pair ofvertical side panels and being open at the top and bottom, means forsecuring said rear panel to said wall, a diaphragm plate extendinghorizontally entirely across said housing and dividing said housing intoan upper compartment and a lower compartment, said diaphragm platehaving a pair of circular openings therein affording communicationbetween said upper compartment and said lower compartment, means on saiddiaphragm plate cylindrical shrouds around said openings and dependinginto said lower compartment, supports extending across said housing andspanning said openings, means for rigidly uniting said diaphragm plateand said supports, electric motors within said upper compartment andrigidly secured to said supports, fans mounted on said motors anddisposed within said shrouds, means for joining adjacent dependingportions of said shrouds, a

pair of panels extending across and supported in said lower compartment,each being disposed beneath one of said fans and each defining verticalair directing passage Ways, means for supporting said panels in saidhousing at a variable lateral inclination, a plurality of louvers insaid lower compartment beneath said anels, and means for supporting saidlouvers in said housing at variable longitudinal inclination.

2. A door air screen as in claim 1 in which said panels are comprised ofhexagonal cellular material forming vertical air directing passageways.

3. A door air screen as in claim 1 in which said diaphragm plate, saidsupports, said shrouds and said means for joining adjacent dependingportions of said shrouds are rigidly connected to form a stiff beamsupport for said motors and said fans.

References Cited by the Examiner UNITED STATES PATENTS ROBERT A. OLEARY,Primary Examiner.

JOHN F. OCONNOR, Examiner.

1. A DOOR AIR SCREEN FOR USE ON A WALL OVER A DOORWAY COMPRISING AHOUSING HAVING A VERTICAL FRONT PANEL, A VERTICAL REAR PANEL, A PAIR OFVERTICAL SIDE PANELS AND BEING OPEN AT THE TOP AN BOTTOM, MEANS FORSECURING SAID REAR PANEL TO SAID SIDE WALL, A DIAPHRAGM PLATE EXTENDINGHORIZONTALLY ENTIRELY ACROSS SAID HOUSING AND DIVIDING SAID HOUSING INTOAN UPPER COMPARTMENT AND A LOWER COMPARTMENT, SAID DIAPHRAGM PLATEHAVING A PAIR OF CIRCULAR OPENINGS THEREIN AFFORDING COMMUNICATIONBETWEEN SAID UPPER COMPARTMENT AND SAID LOWER COMPARTMENT, MEANS ON SAIDDIAPHRAGM PLATE CYLINDRICAL SHROUDS AROUND SAID OPENINGS AND DEPENDINGINTO SAID LOWER COMPARTMENT, SUPPORTS EXTENDING INTO SAID HOUSING ANDSPANNING SAID OPENINGS, MEANS FOR RIGIDLY UNITING SAID DIAPHRAGM PLATEAND SAID SUPPORTS, ELECTRIC MOTORS WITHIN SAID UPPER COMPARTMENT ANDRIGIDLY SECURED TO SAID SUPPORTS, FANS MOUNTED ON SAID MOTORS ANDDISPOSED WITHIN SAID SHOURDS, MEANS FOR JOINING ADJACENT DEPENDINGPORTIONS OF SAID SHROUDS, A PAIR OF PANELS EXTENDING ACROSS ANDSUPPORTED IN SAID LOWER COMPARTMENT, EACH BEING DISPOSED BENEATH ONE OFSAID FANS AND EACH DEFINING VERTICAL AIR DIRECTING PASSAGEWAYS, MEANSFOR SUPPORTING SAID PANELS IN SAID HOUSING AT A VARIABLE LATERALINCLINATION, A PLURALITY OF LOUVERS IN SAID LOWER COMPARTMENT BENEATHSAID PANELS, AND MEANS FOR SUPPORTING SAID LOUVERS IN SAID HOUSING ATVARIABLE LONGITUDINAL INCLINATION.